Control circuits for electric starting mechanism



v 3. 1969 A. H. SEILLY 3,469,106

CONTROL CIRCUITS FOR ELECTRIC STARTING MECHANISM Filed Aug. 30, 1966 United States Patent US. Cl. 290-38 2 Claims ABSTRACT OF THE DISCLOSURE A control circuit for an electrical starting mechanism in which a pinion driven by a motor is, via a first solenoid moved into engagement with a toothed wheel and the circuit includes a current sensitive relay through the coil of which current passes to the motor and normally open contacts operable by the magnetic field produced by the coil control the current flow to the solenoid. The current flowing to the solenoid passes through a manually operable switch and a second solenoid operates a motor controlling switch in series with the motor with the second solenoid being energized by operation of the manually operable switch so that with the latter switch closed, the first solenoid is de-energised when the current flowing through the motor falls below a predetermined value.

This invention relates to control circuits for controlling the operation of electric starting mechanism of the kind including an electric motor, a pinion arranged to be driven by the motor and movable into engagement with a toothed wheel and a solenoid for effecting said movement.

The object of this invention is to provide a control circuit for such a mechanism in a simple and convenient form.

In the accompanying drawings:

FIGURE 1 is a circuit diagram showing one example of a control circuit in accordance with the invention and FIGURE 2 is a circuit diagram showing a modification of the control circuit of FIGURE 1.

One example of a starting mechanism with which the control circuit of the invention may be used comprises an electric motor having an extended armature shaft upon the projecting end of which is formed a quick pitch screw thread. Mounted on the shaft is an axially movable sleeve having a thread complementary to the thread on the shaft with which it is engaged. Formed on the sleeve is a pinion which is engageable with a toothed wheel of the engine and also provided is a solenoid having an armature engageable with the sleeve. The arrangement is such that when the solenoid is energised axial movement will be imparted to the pinion thereby to cause same to be engaged with the toothed wheel of the engine. Furthermore, resilient means is provided so that when the solenoid is de-energised the pinion will be moved out of engagement with the toothed wheel. A mechanism of this general type is described in US. Patent No. 3,124,694 but this mechanism includes in addition its own motor controlling switch which is operable by the armature of the solenoid. This switch is omitted in the present case.

Referring now to FIGURE 1, the field coils of .the motor and its armature 11 are shown connected in series with each other. One terminal of the armature 11 is connected to terminal 8 of a source of DC. supply 12. The other terminal of the field coils is connected to the other terminal 9 of the source of supply by way of the coil of a current relay 13 and a pair of normally open contacts of a motor controlling switch 14. One terminal of the solenoid 15 of the mechanism is connected to terminal 8 and "ice the other terminal is connected through a pair of normally open contacts of the current relay and a normally open manually operable switch 16, to terminal 9 of the source of supply. Also provided is a solenoid 17 which when energised effects closure of the normally open contacts 14, one terminal of the solenoid is connected to terminal 8 and the other terminal to a point intermediate the manually operable switch 16 and the contacts of the current relay 13.

In use, when the manually operable switch 16 is closed the solenoid 17 of the motor controlling switch is energised and the contacts 14 associated therewith close thereby energising the motor. The initial flow of current to the motor is sufiicient to cause the contacts of the current sensitive relay 13 to be closed with the result that the solenoid 15 of the motor is energised and the pinion is moved into engagement with the toothed wheel thereby to effect cranking of the engine. When the engine fires the operator will normally release the manually operable switch 16 and the supply of current to the motor and the solenoid 15 will cease so that the pinion will be moved out of engagement with the toothed wheel of the engine. If however the operator does not release the manually operable switch the current flow to the motor will gradually fall as the speed of the motor increases. When the current falls to a predetermined value the contacts of the current sensitive relay 13 will open and the flow of current to the solenoid 15 will cease thereby allowing the pinion to be moved out of engagement with the toothed wheel partly by the action of the resilient means and partly by the action of the quick screw thread. The motor will however continue to rotate at its light running speed, this speed not being harmful to the rotary parts of the motor.

In the modification of the circuit shown in FIGURE 2 a normally open switch 19 is provided intermediate the field coils 10 and the coil of the current relay. The contacts of the switch are arranged to be closed only when the pinion of the starting mechanism is fully engaged with the toothed wheel of the engine and are positioned within the starter mechanism. Moreover, in parallel with this switch is a resistor 20 through which current flows to the motor when the motor controlling switch 16 is first operated. By this means the motor is initially energised at at low power but when the pinion is fully engaged with the pinion the contacts of the switch 19 are closed and the motor operates at full power to crank the engine. It is essential for the operation of this circuit that the initial flow of current through the resistor is sufficient to cause the contacts of the current sensitive relay 13 to be closed.

Having thus described my invention what I claim as new and desired to secure by Letters Patent is:

1. A control circuit for controlling the operation of an electric starting mechanism of the kind including an electric motor, a pinion arranged to be driven by the motor and movable into engagement with a toothed wheel, and a solenoid for effecting said movement, the control circuit including a current sensitive relay through the coil of which current passes to the motor, a pair of normally open contacts operable by the magnetic field produced by said coil, said contacts serving to control the flow of current to said solenoid, a manually operable switch through which the current flowing to said solenoid flows, a motor controlling switch in series with said motor and a further solenoid for operating the motor controlling switch, said further solenoid being energised by operation of said manually operable switch the arrangement being such that with the manually operable switch held closed the solenoid controlling the pinion will be de-energised when the current flowing through the motor falls below a predetermined value.

2. A control circuit as claimed in claim 1 including a further normally open switch connected in series with 3 Y 4 said motor and which is arranged to be closed when the 2,542,712 2/1951 Schneider et a1. 290-38 pinion has engaged with the toothed wheel and a resistor 3,177,368 4/ 1965 Seilly 290-38 in parallel with said further switch whereby energisation 3,223,863 12/ 1965 Preece et a1 29038 XR of the motor at full power does not occur until the pinion 3,264,483 8/ 1966 Alexander 290-38 has engaged with the toothed wheel. 5 Y

ORIS L. RADER, Primary Examiner References cted G. R. SIMMONS, Assistant Examiner UNITED STATES PATENTS 2,260,742 10/1941 Elkin 290-38 2,443,648 6/1948 Austin et a1. 290-47 

